What is disclosed in PTL 1 has been known as a related electric steering lock device. FIG. 1 shows a configuration of the electric steering lock device described in PTL 1. The electric steering lock device 101 includes: a lock member 160 configured to prohibit the turn of a steering shaft (not illustrated); an electric motor 130 serving as a driving source; and transmission means 140 for transmitting driving force of the electric motor 130 to the lock member while converting rotary motion of the electric motor 130 into linear motion.
The lock member 160 is arranged movably between a locking position at which a tip end of the lock member 160 juts out from a frame 110 and an unlocking position at which the lock member 160 is housed in the frame 110.
The transmission means 140 is formed from: a worm gear 141 placed around a drive shaft 130a of the electric motor 130; a disk-shaped worm wheel 142; a slide gear 145 provided around a center shaft 142a of the worm wheel 142; and a slide nut 146 in threaded engagement with the slide gear 145. The transmission means 140 together with the electric motor 130 is housed in a motor case 185. In the housed state, the transmission means 140 is installed in a housing chamber 112 formed inside the frame 110. An opening of the housing chamber 112 is sealed with a cover 120.
Once the electric motor 130 drives, the rotations of the drive shaft 130a are transmitted to the worm wheel 142 via the worm gear 141, and the worm wheel 142 rotates with the slide gear 145. Once the slide gear 145 rotates, the slide nut 146 moves in an axial direction of the center shaft 142a, and the lock member 160 moves with the slide nut 146.